This disclosure is related to methods for rapid evaluation and selection of hydrogen storage compositions.
Hydrogen is considered to be an ideal fuel for fuel cell vehicles. Typically, hydrogen fuel cells operate by converting the chemical energy in hydrogen and oxygen into water, producing electricity and heat, which electricity is then fed into an electric motor that power a fuel cell vehicle. Pure hydrogen is also a desired for internal combustion engine (ICE) powered vehicles, since it will not produce carbon dioxide, a compound that is widely recognized as the cause of green-house effect. Hydrogen fuel also reduces the emission of aerosol, another pollutant to urban air.
Hydrogen is the most plentiful element in the universe, and is the third most plentiful element on Earth. Hydrogen can be derived from multiple renewable energies. Means of storing hydrogen for end use delivery include: (1) liquid hydrogen, (2) compressed hydrogen, and (3) solid hydrogen storage (i.e., metal hydrides).
Using liquid or gaseous hydrogen as the energy source in a fuel cell is not ideal. Hydrogen is highly flammable and only requires a low hydrogen-to-air concentration for combustion. Furthermore, liquid hydrogen is harder to transport and store than other liquid fuel. Other problems with liquid and gaseous hydrogen storage include low volumetric density, high pressure storage, and high energy cost to compress or liquefy hydrogen. Additionally, there is currently only a very limited infrastructure available for distributing hydrogen to the public.
Solid hydrogen storage materials that chemically store the hydrogen fuel are considered to be an advantageous source of hydrogen for fuel cells, ICEs and in a wide range of potential applications. However, currently known storage materials are generally fraught with deficiencies in one or more desirable characteristics, such as, for example, low storage capacity for hydrogen, unfavorable thermodynamics and/or kinetics for hydrogen absorption and desorption. Therefore, improved hydrogen storage materials are desired for a variety of applications, including fuel cells for vehicles, personal power generation, and stationary power generation.
Extensive research activity in the past 30 or so years has focused on storing hydrogen in the form of solid metal hydrides. Metal hydrides are typically generated exothermically when metals and alloys are exposed to hydrogen. Most often, the hydrogen reacts with these metals or alloys and forms new compounds. The hydrogen can be recovered for use by heating, by electrolytic oxidation of the hydride, or by a reaction with an oxide or water. One advantage of using a metal hydride for hydrogen storage is that the volumetric density for hydrogen storage in metal hydrides is relatively high in comparison to other storage methods.
Examples of well-known hydrogen storage materials include metal hydrides, such as FeTiH2 and LaNi5H6, which hydrides release hydrogen upon heating. Even though FeTiH2 and LaNi5H6 have acceptable hydrogen cycling temperatures, the hydrogen content in terms of weight percent is too low for use in vehicular fuel cell applications. Other metal hydrides, such as MgH2 and TiH2, have higher hydrogen contents, about 7.6 and about 4.0 percent by weight respectively, but must be heated to high temperatures (i.e., above about 300° C.) in order to recover the hydrogen. The preparation of materials for use as hydrogen storage media analyzing them for their potential hydrogen storage capacity is a time consuming process.
In view of the above, there is a need for safer, more effective methods of storing and recovering hydrogen. In addition, there is a desire to minimize the overall system volume and weight. There is also a need for a rapid synthesis and evaluation method for determining the hydrogen storage capacity in any material to facilitate new material discovery in the field of hydrogen storage.